Mechanical sound recording apparatus



y 1938. J. J. HARDENBERG 2,118,347

MECHANICAL SOUND RECORDING APPARATUS Filed Sept. 28. 1936 Jeff/JEDE/VBEEG flrrd 5 /1/15 y Patented May 24, 1938 UNITED STATES 2,118,347MECHANICAL SOUNI I IIIESECORDING APPARA- Jan Jesayas Hardenberg,Eindhoven, Netherlands, assignor to N. V. Philips Gloeilampenfabrieken,Eindhoven, Netherlands Application September 28, 1936, Serial No.103,039 In Germany September 30, 1935 '8 Claims.

My invention relates to mechanical sound re cording apparatus and moreparticularly to a driving device for use in such apparatus.

To insure satisfactory recording it is essen-' tial that the film bemoved past the recording point at a very constant speed, and althoughvarious types of driving devices have been proposed for this purpose,such devices are unsatisfactory for mechanical recording due to therelatively large recording forces exerted on the film. If the devicecomprises a toothed roller to drive the film at the recording point, thespeed of the film, due to the film becoming more or less wrinkled forone reason or another, will be made irregular by tooth frequencies. Ifintermediate driving gears are used they may introduce disturbing toothfrequencies, and in ad-. dition such gears are expensive as they must bevery accurately out. On the other hand if a friction drive is used formechanical recording,

the active surface of the friction driving wheel may become worn inspots due to the high starting forces, with the result that the speed ofthe film becomes irregular.

The above difiiculties are particularly severe in mechanically recordingon a film, one or more sound tracks whose width variations areappreciable enlargements of the depth variations, and my invention isparticularly advantageous for use in this type of recording. Such a typeof recording has been described in U. S. Patent No. 1,919,116, to JamesA. Miller, in which a V- shaped cutting tool having an apical angle ofabout 174 is used, and which tool exerts upon the film a variablerecording force, for instance, up to about 30 pounds per square inch.Prior recording devices using at the recording point a roller directlycoupled to a flywheel driven through a mechanical filter from a drivingmotor do not give satisfactory results in this type of recording,because with the extremely high recording forces, the mass of theflywheel and the elasticity of the mechanical filter bring about naturalvibrations which constitute a serious drawback. To eliminate thisdifficulty the mechariical filter would have to have the contradictoryproperties of being sufficiently elastic to absorb any disturbing toothfrequencies and of being sufficiently rigid to prevent the varyingrecording forces from causing deleterious vibrations.

The object of my invention is to overcome the above difliculties and toprovide a simple and inexpensive driving device for mechanical recordingapparatus by which a very uniform film speed at the recording point isinsured without any flywheel. i

In accordance with the invention I drive the film at the recording pointby a smooth or nontoothed recording roller driven from a driving motorthrough a friction drive cooperating with a large diameter driving wheelhaving a small mass, fixed on the shaft of the recording roller.

To eliminate any irregularities in the film speed due to uneven wearingof the friction surface, I provide two friction driving wheels driven bythe motor and adapted to be selectively placed into engagement with thedriving wheel. One of the friction wheels, referredto hereinafter as thestarting friction wheel, engages the driving wheel only while therecording roller is being accelerated to the normal recording speed. Thesecond friction wheel, referred to hereinafter as the running frictionwheel, serves to drive the film during the recording and is adapted toen-- gage the driving wheel only after the recording roller has reached,or substantially reached, its

normal running speed. The friction wheels may be selectively placed intoengagement with the driving wheel either manually or automatically andin the latter case I provide a mechanism interconnected with the starterof the driving motor, whereby operation of the starter controls theengagement of the friction wheels.

Further features and advantages of my invention will appear as thedescription progresses.

In order that my invention may be clearly understood and readily carriedinto effect, I shall describe same more fully with reference to theaccompanying drawing in which:

Figure 1 is a sectionized view of a portion of a recording deviceembodying a driving device according to the invention.

Fig. 2 isa sectionized view of a portion of a recording deviceillustrating another embodiment of the invention.

Fig. 2a is a view of a portion of Fig. 1 showing a modified bearing.

Fig. 3 is a partly sectionized view of a portion of a recording deviceusing a drivingdevice according to another embodiment of the invention.

Fig. 4 is a view along line 4-4 of Fig. 3.

Fig. 5 is a view along line 55 of Fig. 4.

The device shown in Fig. 1 comprises a rotatably-mounted shaft 2carrying a driving wheel I and a smooth-faced recording roller 30driving a film 3| upon which a sound track is to bemechanicallyrecorded. For clarity, the recording tool and actuatingmechanism therefore are not shown but these may be of any type used formechanical recording.

Pivotally mounted at I on a lever 32 so as to be rotatable in thedirection of arrow 40 is a driving motor 5 having a shaft 4 upon whichare fixedly mounted a starting friction wheel 3 having a beveled activesurface cooperating with the conical surface 9 of the driving wheel, anda running friction wheel 8 adapted to engage the cylindrical surface 33of the driving wheel. The motor 5 is preferably a synchronous motor withasynchronous starting.

Lever 32 is pivoted at 34 to a fixed support whereby the motor 3 may bemoved in the direction of arrow 42 to thereby disengage wheel 3 fromsurface 3. Secured with one end to the upper end of the motor and withits other end fixed, is a tension spring 6 serving to hold wheel 3 incontact with the surface 9 when the apparatus is in the position shown,and to bring wheel 8 into contact with surface 33 when the motor ismoved in the direction of arrow 42 by lever 32.

As shown, the device is in its starting position with the starting wheel3 driving the driving wheel I, and when driving wheel I and roller 30have acquired approximately normal running speed, the motor is moved bylever 32 in the direction of arrow 42 to thereby bring wheel 3 intoengagement with surface 33 to thus drive wheel I during the normalrunning of the device.

In such a friction drive, any desired transmission ratio may be readilyobtained by suitably selecting the diameters of the friction wheels andof the driving wheel, and in addition toothed recording rollers andtransmission gears are dispensed with, thereby avoiding disturbing toothfrequencies. i

To decrease the driving force exerted by the wheels 3 and 3, I give thesurfaces 9 and 33 of the driving wheel I a large diameter, for instanceabout 8 inches and preferably about 16 inches.

This also reduces the degree to which shocks or unevenness in therotational speed of the driving wheel are transmitted to the recordingroller 33 and thus reduces disturbances at the recording point. Toinsure an accurate mechanical sound record, the diameter of roller 30must be above a minimum value, and thus the smallest diameter of thedriving wheel to secure the above results is determined thereby.

The active surface of the running friction wheel 8 is preferably made ofa flexible material, such as rubber, which materially dampens the shockand is preferably rounded to give a better frictional contact. Due tothe use of the separate .starting wheel 3, such a rounded surface can beused without the danger of uneven wear thereon.

From the above it is seen that the protrusive or accelerating driving iseffected only by the starting wheel 3 and thus only the surface of thiswheel can be effected thereby, whereas the surface of wheel 8 willretain its circular shape.

Fig. 2 illustrates the driving device of Fig. 1 as applied to asound-film reproducing and recording device such as is used in broadcaststudios and the like. In this figure the shaft 2 carrying the drivingwheel I is rotatably supported in an oblique manner by a bearing H. Theshaft 2 passes through a stationary supporting plate l0 upon which aiemounted the various rollers, film spools, sound scanning device, etc.(not shown).

The weight of the driving wheel 10 is represented by the vector G havingcomponents A and B; the component B causing undesirable wear on one sideof the bearing whereas component A acts on the bottom of the bearing. Byusing the driving device according to the invention a force C oppositein direction to force B is exerted on the wheel I and by suitablyarranging the device the force C may be made equal to force B andeliminates same. Thus, only the force A remains active, which force isless than the weight as represented by vector G.

The bearing H and the cooperating portion of the shaft 2 may be taperedupward and the s aft switch of the motor. In this figure the motor 5 ismounted with the interposition of a rubber pad l2 to prevent the ,motorvibrations being transmitted to the supporting plate and recordinginstruments upon a supporting bracket 36 having two arms l3 fixedlysecured to a rod l4. The rod i4 is rotatably supported so as to beslidable in its axial direction by two bearings l5 fixedly mounted on asuitable support. Secured to rod l4 are two disc-shaped guides l6cooperating with a roller l1 fixed to a lever l8. (See Fig. 4.)

A spring 23 having one end fixed and its other end secured to the motor5 exerts an upward force on the motor approximately equal to the weightof the motor and the parts; attached thereto to keep the motor floating.The spring 23 also serves to hold the friction wheel 3 against thesurface 3 and for this purpose its fixed end is mounted to the rear ofthe plane of the drawing.

The motor 5, which is preferably a synchronous motor with asynchronousstarting, receives cur-v rent through a starting switch 31 from a supply38 into engagement with the surface 33 by the action of spring 23; themotor being rotated slightly about the axis of rod l4. This movement iseffected automatically by operation of the starter 31, and for this,purpose, as shown in Figs. 4 and 5, the lever I8 is pivoted at I9 andprovided at its end with a roller 20 cooperating with a spiral slot 24in a disc 2| connected to the shaft 22 of starter 31.

As shown in Figs. 4 and 5, the roller 20 is in the circular part of theslot 24 whereby lever I8 is in the position shown in Fig. 4 and themotor and wheels 3 and 8 are in the starting position as shown in Fig.3. Upon rotation of the starter shaft 22 into the'running position ofthe motor, cam 2| is turned in the direction of the arrow 46 wherebyroller 20 and the end of lever l8 are moved in the direction of thearrow 41. This moves rod l4 in the direction of the arrow 39 whereby themotor is lowered, wheel 3 is disengaged from surface 9, and wheel 8 isbrought into engagement with surface 33 by the action of spring 23.

While I have described my invention in connection with specific examplesand applications, I'do not wish to be limited thereto but desire theappended claims to be construed as broadly as permissible in view of theprior art.

What I claim is:

1. A mechanism for driving a film at the sound-recording or reproducingpoint, comprising a film-driving roller, a wheel rotatable with saidroller and having a driving surface, a shaft, a motor for driving saidshaft, two friction wheels mounted on said shaft and adapted toselectively engage said surface, and means to move said, shaft tothereby bring one of said friction wheels into engagement with saidsurface only during driving surface having a diameter greater than 8inches, a shaft, a synchronous motor with asynchronous starting fordriving said shaft, two friction wheels mounted on said shaft andadapted to selectively engage said surface, and means to move said shaftto thereby bring one of said friction wheels into engagement with saidsurface only during starting of the mechanism and to bring the otherfriction wheel into engagement with said surface only during normalrunning of the mechanism.

3. A mechanism for driving a film at the sound-recording or -reproducingpoint, comprising a driving wheel provided with a large-diameter drivingsurface having a cylindrical portion and a conically-shaped portion, asmooth-faced filmdriving roller rotatable with said driving wheel, adriving motor, a running friction wheel driven by said motor and havinga rounded surface, a starting friction wheel driven by said motor andhaving a beveled surface, and means to bring the beveled surface of saidstarting wheel into engagement with the conically-shaped portion of saiddriving surface only during the starting of the mechanism and to bringthe rounded surface of said running wheel into engagement with thecylindrical portion of said driving surface only during normal runningof the mechanism.

4. A driving mechanism for driving a film at the sound-recording or-reproducing point, comprising a driving wheel having a large-diameterdriving surface, a smooth-faced film-driving roller rotatable with saiddriving wheel, a driving motor, a power supply system for said motorincluding a starting device, two friction wheels driven by said motorand adapted to selectively engage said driving surface, and-meanscontrolled by said starting device to bring one of said wheels intoengagement with said driving surface only during starting'of themotor'and to bring the other wheel into engagement with said drivingsurface only during normal running of the motor.

5. A mechanism for driving a film at the sound-recording or -reproducingpoint, comprising a driving wheel provided with a large-diameter'drivingsurface, a smooth-faced film-driving roller directly driven by saiddriving wheel, a synchronous driving motor with asynchronous startingand having a shaft, two friction wheels fixedly mounted on said shaftand adapted to selectively engage said driving surface, mounting meansfor said motor permitting lateral and axial displacement thereof andincluding a resilient member counterbalancing the weight of the motorand forcing the friction wheels in the direction of said drivingsurfaces, and means connected with said mounting means to bring one ofsaid friction wheels into engagement with said driving surface onlyduring the starting of the mechanism and to bring the other frictionwheel into engagement with the driving surface only during normalrunning of the mechanism.

6. A -mechanism for driving a film at the sound-recording or-reproducing point, comprising a driving wheel provided with alarge-diameter driving surface having a cylindrical portion and aconically-shaped portion, a smooth-faced film-driving roller rotatablewith said driving wheel, a synchronous driving motor with asynchronousstarting and having a shaft, a power supply for said motor including astarting device, a starting friction wheel having a beveled activesurface adapted to contact said conicallyshaped portion, a runningfriction wheel having a rounded active surface adapted to contact saidcylindrical portion, said friction wheels being fixedly mounted on saidmotor shaft, mounting means for said motor permitting lateral and axialdisplacement thereof and including a resilient member counterbalancingthe weight of the motor and forcing said friction wheels toward saiddriving surfaces, and means connected to said mounting means andactuated by said starting device to place said starting friction wheelin engagement with the coni-cally-shaped driving surface only during thestarting of the mechanism and to place said running friction wheel inengagement with the cylindrical driving surface only during normalrunning of the mechanism.

7. A mechanism for driving a film at the sound-recording or -reproducingpoint, comprising a driving wheel provided with a large-diameter drivingsurface having a cylindrical portion and a conically-shaped portion, asmooth-faced film-driving roller rotatable with said driving wheel, asynchronous driving motor with asynchronous starting and having a shaft,a power supply for said motor including a starting device, a startingfriction wheel having a beveled active surface adapted to engage saidconicallyshaped portion, a running friction wheel having a roundedsurface adapted to engage said cylindrical portion, said friction wheelsbeing fixedly mounted on said motor shaft, mounting means for said motorpermitting rotational and axial movement thereof and including aresilient member counterbalancing the weight of the motor and forcingsaid friction wheels in the direction of said driving surface, and meansto bring said starting friction wheel into engagement with the conicalsurface portion only during the starting of the mechanism and to bringsaid running friction wheel into engagement with the cylindrical surfaceportion only during normal running of the mechanism, said latter meanscomprising a cam connected to said starting device, and a membercontrolled by said cam and controlling the position of said motor andfriction wheels.

8. A driving mechanism for driving at the recording point a film to bemechanically recorded, comprising a driving wheel having alarge-diameter driving surface, a smooth-faced film-driving rollerrotatable with said driving wheel, a shaft, a motor directly connectedto said shaft, two friction wheels mounted on said shaft and adapted tobe selectively placed into engagement with said driving surface, andmeans to move said shaft to thereby place one of said friction wheels inengagement with said driving surface only during the starting of themechanism and to place the other friction wheel in engagement with saiddriving surface only during normal running of the mechanism.

JAN JESAYAS HARDENBERG.

